The invention relates to an axle modulator of an axle, particularly of a trailer or semi-trailer, having an axle control unit connected to a compressed-air supply.
In the case of trailers or semi-trailers, it is known to construct the service brake system, as a pneumatic power braking system which acts on the front and rear axle of the trailer. When the driver in the towing vehicle operates the service brake system or the no-linkage parking brake system, the braking pulses transmitted by the pressure rise in the brake line actuate a trailer brake valve such that compressed air flows from an air brake reservoir by way of a brake power controller into the brake cylinders of the front axle and rear axle. The input brake pressure is at a defined ratio to the control pressure in the brake line. The brake power controller mechanically regulated by way of the front axle automatically adapts the brake pressure for the front and rear axle of the trailer to the axle load.
In addition, it is known to provide an air suspension on the axle of the trailer or semi-trailer. Air spring valves regulate the air quantity in the air springs corresponding to the loading of the trailer. They thereby have the result that the distance between the trailer body and the road remains the same irrespective of the loading of the trailer. The air suspension is separate from the braking system of the trailer or the semi-trailer. The only contact point is the common compressed-air supply from the towing vehicle by way of jointly utilized compressed-air reservoirs.
It is an object of the invention to provide a fully integrated axle system, which has a simple construction and can be mounted without any special configuration on the frame of the semi-trailer or trailer.
According to the invention, this object is achieved by providing an axle modulator of an axle, particularly of a trailer or semi-trailer, having an axle control unit which is connected to a compressed-air supply. The axle control unit includes a first and a second valve, the first valve controlling a service brake and the second valve controlling an air suspension. Further and advantageous developments are described and claimed herein.
A high degree of integration is achieved as a result of the fact that, according to the invention, a first and a second valve are provided in an axle control unit of an axle modulator of an axle, which axle control unit is connected to the compressed-air supply. The first valve controls a service brake and the second valve controls an air suspension. In contrast to the state of the art, fewer separate components are required, which also saves costs. The trailer or semi-trailer can be produced independently of the tractor vehicle to which the trailer is to be hitched. By means of the axle control unit, the service brake with the ABS function as well as the air suspension can be operated. The axle modulator controls the pressure in the wheel braking devices on both sides of the axle.
The valves of the axle control unit are advantageously controlled electronically. As a result of this measure, only electronic pulses still have to be transmitted from the towing vehicle for triggering the service brake. This control is more reliable than the control by means of the pressure rise in the brake line of transmitted brake pulses. A conventional brake line can therefore be eliminated. An electronic control of the second valve for the air suspension permits a faster reaction to the actual operating conditions of the trailer or semi-trailer.
It is particularly preferable for software to be arranged in the axle modulator for regulating the air suspension. This measure permits the installing of the software together with the axle or the axle modulator. The installation of an additional memory for the software in or on the trailer is not necessary. In particular, the software for regulating the air suspension as well as the software for regulating the antilock system (ABS) can be stored in the axle modulator. As a result, a further integration of the braking system and of the air suspension is achieved, on the one hand. On the other hand, a modular system is created, which can easily be mounted and exchanged. This accelerates the assembly of a trailer.
It is particularly advantageous for the above-described axle modulator to be assigned to each axle arrangement. As a result, the service brake and the air suspension can be controlled and regulated individually for each axle arrangement. An axle system integrated in this manner can easily and rapidly be mounted and wired to the frame of a trailer.
In a preferred further development, a suspension for the axle arrangement is provided, in which suspension the electronic control system for the axle modulator is arranged. It is particularly preferable for the suspension to comprise a hollow U-carrier, in which the electronic control system is arranged. On the one hand, the electronic control system is thereby disposed in a protected manner. On the other hand, it is mounted without additional mounting expenditures together with the axle arrangement on the trailer or semi-trailer.
In a preferred embodiment of the invention, a first sensor system is provided, which is connected with the electronic control system and which detects the actual spring excursion of the entire axle and/or of both wheel sides separately. The actual spring excursion is read-in as a controlled variable. As a function of the determined spring excursion, the second valve for the air suspension can be controlled. When the spring excursion is detected on both wheel sides, a rolling of the trailer can be detected, and a corresponding controlling of the second valve can counteract this rolling.
Preferably, a second sensor system is provided for detecting the coefficients of friction of both wheels of the axle arrangement, which is connected with the electronic control system. On the basis of the measured coefficients of friction, a suitable controlling of the first valve can take place. Particularly, the ABS braking function can be optimized. In the case of a slight difference in the coefficient of friction between the right and the left wheel of an axle, the brake pressure is controlled onto the wheel with the higher adhesion level. Thus, although one wheel locks, the other wheel can convert the full braking power. In this manner, the braking distance can be shortened.
A secure braking of the trailer or of the semi-trailer is ensured in that the compressed-air supply of the axle arrangement includes a compressed-air reservoir.
It is particularly preferable for the compressed-air reservoir to be arranged in the interior of the axle body of the axle. Thus, a separate compressed-air reservoir is assigned to each axle. When the axle is mounted, a respective compressed-air reservoir is therefore also mounted in each case. Furthermore, the provision of a compressed-air reservoir has the advantage that the axles can be braked and sprung independently of one another, and the trailer can also be stopped in the event of a failure of the compressed-air supply.
In a particularly preferred embodiment, an overflow valve is arranged, which has a limited return flow and by way of which the compressed-air reservoir is connected to a pressure supply line. As a result of this measure, the individual axles can communicate with one another because they are connected to a common supply line. However, the overflow valve has the effect that, in the event of a pressure drop in the supply line, a reliable braking of the trailer can still be carried out because sufficient compressed air is stored in the compressed-air reservoir in order to be able to stop the trailer.
A particularly good spring suspension of the trailer is achieved when the air suspension for each wheel includes bellows. Thus, the suspension can be adjusted independently for each side of an axle. In particular, this measure makes it possible to counteract a rolling of the trailer.
Pressure sensors are preferably provided for detecting the internal pressure of the bellows. As a result of this measure, the loading condition of the trailer or semi-trailer can be detected. On the other hand, a load-dependent brake power control can be implemented.
In a particularly preferred embodiment, a valve arrangement is provided, which is connected with the pressure sensors and which, as the internal pressure of the bellows increases, bleeds the bellows and feeds compressed air to lifting bellows. This lifting axle function can be controlled by the second valve of the axle control unit. As the weight decreases, the necessary internal pressure in the air bellows will drop. Starting at a defined threshold, the lifting of the axle will be triggered. In this manner, a constant distance of the frame of the semi-trailer to the ground can be implemented. When the axle is lifted, the air pressure in the bellows is released for the bleeding and the stored pressure fed into lifting bellows, which lift the axle. The valve arrangement advantageously comprises a 4/2 valve.
Embodiments of the invention will be explained in detail by means of the drawings.